Growth in demand for Wireless Local Area Networks (WLANs) is driving the development of new technology to provide higher throughput. To a greater extent this growth is due to the increased number of users and applications desiring wireless transmission and to a lesser extent to the emergence of new applications needing higher transmission rates along a single connection between two points. Previous work has focused on increasing link throughput. This is necessary for single-stream high throughput applications. While it helps increase aggregate throughput, it is not the only way to do so. A Media Access Control (MAC)-based approach that enables the parallel use of multiple channels in a BSS, or a wireless mesh, can increase aggregate throughput. The CCC (Common Control Channel) MAC protocol utilizes two types of logical channels, the control channel and the data channels.
In wireless Local Area Networks (LANS), a wireless channel can be reserved for the transmission of a sequence of frames while employing asynchronous distributed random channel access methods. In such an environment, both the source and destination of the transmission broadcast the reservation duration in order to establish the interference neighborhood.
One method of performing reservation in wireless LANs is by utilizing Frame-by-frame reservation. According to the 802.11 distributed channel access MAC protocol, RTS/CTS frames are used to notify neighbors of the start of the reservation. The reservation time is extended on a frame-by-frame basis, by updating the duration of the reservation with each data frame and the acknowledgement that follows. A consequence of frame-by-frame reservation if that, if the reservation is denied, it does not require cancellation.
Another method of performing reservation in wireless LANS is by utilizing Start-to-finish reservation. If it is not be possible to extend the time of channel reservation on a frame-by-frame basis, the channel must be reserved for the entire sequence of transmissions, start to finish, at the time of the reservation request, and, if the reservation request is denied, or if time remains reserved at the completion of transmission, the reservation must be cancelled.
A start-to-finish reservation applies to any combination of nodes (i.e. mesh points/APs/stations). A node reserves a channel to cover an entire sequence of transmissions, directed to either one or various different destinations, possibly including responses from the destinations. If the reservation is not authorized, or when the transmission sequence is completed, the reserving node releases the remaining reservation time by canceling the reservation.
An example of this is given using a Mesh Coordination Function (MCF) example comprising a mesh network with multiple channels. Reservations for time on one of multiple channels occur asynchronously by an exchange of frames on the control channel. All mesh points monitor the same channel—called the “control” channel. Because the control channel is different from the “traffic” channel (the channel of the data transmission) it is not possible to extend a reservation on a frame-by-frame basis. The traffic channel is thus reserved for the total time needed to transmit the data frames.
Another example is given using an 802.11e hybrid polled and distributed access 802.11e systems. When a polling cycle is started by a Hybrid Controller (HC, also referred to as an Access Point), it reserves the channel for the entire duration of the service period
A NAV is defined as a time period a node must refrain from transmitting on a traffic channel. A reservation request from the source is either granted or denied by the destination, and notice is sent to the source. The response contains the remaining reservation duration in order to notify the neighbors of the destination node. To avoid collisions, each node keeps a NAV for each traffic channel which is set according to the received reservation requests and responses. The NAV is the time period the node must refrain from transmitting on the channel, and is updated when a node receives a reservation request or a response to the reservation request.